There has been a tremendous interest in carbon nanoparticles since the discovery of the carbon nanotube in a high-temperature arc. Concentric shell structures, 3-7 nm in diameter, have been observed in small, spherical particles of graphitized carbon deposited during the evaporation of carbon by arc discharge in vacuum.
It has been reported that when irradiating carbon soot, collected from an arc-discharge apparatus, in a 300 KV-transmission electron microscope (TEM), with an electron dose 10-20 times higher than under normal operating conditions, the originally tubular or polyhedral graphite particles start becoming spherical after 10 minutes of irradiation, and eventually completely transformed into a quasi-spherical morphology. It was further reported that the particles were composed of an assembly of concentric spherical graphitic cages with the distance between layers being that of bulk graphite (0.34 nm). The assembly of spherical shells obtained were on the order of 47 nm in size. Additionally, it has also been shown that electron irradiation at 700° C. could also anneal out defects resulting in spherical shells with a decreasing spacing towards the center of the onion.
More recently, a dc arc discharge employed in de-ionized water between two carbon electrodes produced nested onion-like carbon nanoparticles with diameters of 4-36 nm. In addition to spherical nano-onions, elongated structures have been reported. Other carbon structures have also been observed both in Nd:YAG laser ablation and CO2 laser ablation of graphite rods. These include nanohorns. Nearly spherical particles about 80 nm in diameter were observed and individual particles showed aggregates of horn-shaped sheaths of single-walled graphene sheets in high resolution. Carbon nanotubular structures have been observed using KrF laser irradiation of a graphite pellet at 248 nm at 1150° C. and high argon gas pressure (500 Torr).
It would be useful to be able to provide carbon nanostructures without having to employ a high temperature process. It would be useful to be able to use an excimer laser to provide carbon nanostructures without having to employ a high temperature process. It would be useful to be able to provide larger sized carbon nanostructures than those produced by presently known techniques.